blocks|key|2864777|text|只是解决了这个问题。在深入研究了更长一段时间后，我发现了this+SO+post，它涵盖了完全相同的情况。这让我走上了正确的道路。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2864778|基本上，如果包含派生类作为额外类型，则XmlSerializer需要知道默认名称空间。发生这种情况的确切原因尚不清楚，但序列化现在仍在工作。|style|CODE|BOLD|2864779|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/4616505/is-there-a-reason-why-a-base-class-decorated-with-xmlinclude-would-still-throw-a^0|S|C|0|0|J|D|16|S|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|6|7|U|8|@$A|V|B|W|F|G]|$A|X|B|Y|F|H]]|9|@]|C|$]]|$1|I|3|-4|5|6|7|Z|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Just solved the issue. After digging around for a while longer, I found <a href="https://stackoverflow.com/questions/4616505/is-there-a-reason-why-a-base-class-decorated-with-xmlinclude-would-still-throw-a">this SO post</a> which covers the exact same situation. It got me in the right track.

Basically, the <code>XmlSerializer</code> needs to know the default namespace if derived classes are included as extra types. The exact reason why this has to happen is still unknown but, still, serialization is working now.

blocks|key|214783|text|这对我很有效：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|214784|[XmlInclude(typeof(BankPayment))]
[Serializable]
public+abstract+class+Payment+{+}++++

[Serializable]
public+class+BankPayment+:+Payment+{}+

[Serializable]
public+class+Payments+:+List<Payment>{}

XmlSerializer+serializer+=+new+XmlSerializer(typeof(Payments),+new+Type[]{typeof(Payment)});|code-block|syntax|javascript|214785|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This worked for me:

<pre><code>[XmlInclude(typeof(BankPayment))]
[Serializable]
public abstract class Payment { } 

[Serializable]
public class BankPayment : Payment {} 

[Serializable]
public class Payments : List&lt;Payment&gt;{}

XmlSerializer serializer = new XmlSerializer(typeof(Payments), new Type[]{typeof(Payment)});
</code></pre>

blocks|key|2864808|text|基于this，我能够通过改变我正在使用的XmlSerializer的构造函数来解决这个问题，而不是改变类。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2864809|而不是使用这样的东西(在其他答案中建议)：|2864810|[XmlInclude(typeof(Derived))]
public+class+Base+{}

public+class+Derived+:+Base+{}

public+void+Serialize()
{
++++TextWriter+writer+=+new+StreamWriter(SchedulePath);
++++XmlSerializer+xmlSerializer+=+new+XmlSerializer(typeof(List<Derived>));
++++xmlSerializer.Serialize(writer,+data);
++++writer.Close();
}|code-block|syntax|javascript|2864811|我这样做了：|2864812|public+class+Base+{}

public+class+Derived+:+Base+{}

public+void+Serialize()
{
++++TextWriter+writer+=+new+StreamWriter(SchedulePath);
++++XmlSerializer+xmlSerializer+=+new+XmlSerializer(typeof(List<Derived>),+new[]+{+typeof(Derived)+});
++++xmlSerializer.Serialize(writer,+data);
++++writer.Close();
}|2864813|entityMap|0|LINK|mutability|MUTABLE|url|https://social.msdn.microsoft.com/Forums/en-US/83181d16-a048-44e5-b675-a0e8ef82f5b7/why-do-i-have-to-xmlinclude-derived-classes-in-order-to-serialize?forum=asmxandxml^0|K|D|2|4|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@$9|11|A|12|1|13]]|E|$]]|$1|F|3|G|5|6|7|14|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|15|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|16|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|17|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

Base on <a href="https://social.msdn.microsoft.com/Forums/en-US/83181d16-a048-44e5-b675-a0e8ef82f5b7/why-do-i-have-to-xmlinclude-derived-classes-in-order-to-serialize?forum=asmxandxml" rel="noreferrer">this</a> I was able to solve this by changing the constructor of <code>XmlSerializer</code> I was using instead of changing the classes.

Instead of using something like this (suggested in the other answers):

<pre><code>[XmlInclude(typeof(Derived))]
public class Base {}

public class Derived : Base {}

public void Serialize()
{
 TextWriter writer = new StreamWriter(SchedulePath);
 XmlSerializer xmlSerializer = new XmlSerializer(typeof(List&lt;Derived&gt;));
 xmlSerializer.Serialize(writer, data);
 writer.Close();
}
</code></pre>

I did this:

<pre><code>public class Base {}

public class Derived : Base {}

public void Serialize()
{
 TextWriter writer = new StreamWriter(SchedulePath);
 XmlSerializer xmlSerializer = new XmlSerializer(typeof(List&lt;Derived&gt;), new[] { typeof(Derived) });
 xmlSerializer.Serialize(writer, data);
 writer.Close();
}
</code></pre>

blocks|key|217726|text|只需在Base中完成，这样任何孩子都可以被序列化，更少的代码更干净的代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|217727|public+abstract+class+XmlBaseClass++
{
++public+virtual+string+Serialize()
++{
++++this.SerializeValidation();

++++XmlSerializerNamespaces+XmlNamespaces+=+new+XmlSerializerNamespaces(new[]+{+XmlQualifiedName.Empty+});
++++XmlWriterSettings+XmlSettings+=+new+XmlWriterSettings
++++{
++++++Indent+=+true,
++++++OmitXmlDeclaration+=+true
++++};

++++StringWriter+StringWriter+=+new+StringWriter();

++++XmlSerializer+Serializer+=+new+XmlSerializer(this.GetType());
++++XmlWriter+XmlWriter+=+XmlWriter.Create(StringWriter,+XmlSettings);
++++Serializer.Serialize(XmlWriter,+this,+XmlNamespaces);
++++StringWriter.Flush();
++++StringWriter.Close();

++++return+StringWriter.ToString();

++}

++protected+virtual+void+SerializeValidation()+{}
}

[XmlRoot(ElementName+=+"MyRoot",+Namespace+=+"MyNamespace")]
public+class+XmlChildClass+:+XmlBaseClass
{
++protected+override+void+SerializeValidation()
++{
++++//Add+custom+validation+logic+here+or+anything+else+you+need+to+do
++}
}|code-block|syntax|javascript|217728|这样，无论在什么情况下，您都可以在子类上调用Serialize，并且仍然能够在对象序列化之前执行所需的操作。|217729|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Just do it in the Base, that way any child can be Serialized, less code cleaner code.

<pre><code>public abstract class XmlBaseClass 
{
 public virtual string Serialize()
 {
 this.SerializeValidation();

 XmlSerializerNamespaces XmlNamespaces = new XmlSerializerNamespaces(new[] { XmlQualifiedName.Empty });
 XmlWriterSettings XmlSettings = new XmlWriterSettings
 {
 Indent = true,
 OmitXmlDeclaration = true
 };

 StringWriter StringWriter = new StringWriter();

 XmlSerializer Serializer = new XmlSerializer(this.GetType());
 XmlWriter XmlWriter = XmlWriter.Create(StringWriter, XmlSettings);
 Serializer.Serialize(XmlWriter, this, XmlNamespaces);
 StringWriter.Flush();
 StringWriter.Close();

 return StringWriter.ToString();

 }

 protected virtual void SerializeValidation() {}
}

[XmlRoot(ElementName = "MyRoot", Namespace = "MyNamespace")]
public class XmlChildClass : XmlBaseClass
{
 protected override void SerializeValidation()
 {
 //Add custom validation logic here or anything else you need to do
 }
}
</code></pre>

This way you can call Serialize on the child class no matter the circumstance and still be able to do what you need to before object Serializes.

blocks|key|2864910|text|我同意bizl的观点|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2864911|[XmlInclude(typeof(ParentOfTheItem))]
[Serializable]
public+abstract+class+WarningsType{+}|code-block|syntax|javascript|2864912|另外，如果您需要将这个包含的类应用于对象项，您可以这样做|2864913|[System.Xml.Serialization.XmlElementAttribute("Warnings",+typeof(WarningsType))]
public+object[]+Items
{
++++get
++++{
++++++++return+this.itemsField;
++++}
++++set
++++{
++++++++this.itemsField+=+value;
++++}
}|2864914|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I agree with bizl 

<pre><code>[XmlInclude(typeof(ParentOfTheItem))]
[Serializable]
public abstract class WarningsType{ }
</code></pre>

also if you need to apply this included class to an object item you can do like that

<pre><code>[System.Xml.Serialization.XmlElementAttribute("Warnings", typeof(WarningsType))]
public object[] Items
{
 get
 {
 return this.itemsField;
 }
 set
 {
 this.itemsField = value;
 }
}
</code></pre>

I've got a very strange problem when working with .NET's <code>XmlSerializer</code>. 

Take the following example classes:

<pre><code>public class Order 
{
 public PaymentCollection Payments { get; set; }

 //everything else is serializable (including other collections of non-abstract types)
}

public class PaymentCollection : Collection&lt;Payment&gt;
{
}

public abstract class Payment 
{
 //abstract methods
}

public class BankPayment : Payment
{
 //method implementations
}
</code></pre>

AFAIK, there are three different methods to solve the <code>InvalidOperationException</code> that's caused by the serializer not knowing about the derived types of <code>Payment</code>.

1. Adding <code>XmlInclude</code> to the <code>Payment</code> class definition:

This is not possible due to all classes being included as external references over which I have no control of.

2. Passing the derived types' types during creation of the <code>XmlSerializer</code> instance

Doesn't work.

3. Defining <code>XmlAttributeOverrides</code> for the target property in order to override the property's default serialization (as explained in <a href="https://stackoverflow.com/questions/2689566/how-to-add-xmlinclude-attribute-dynamically">this SO post</a>)

Also doesn't work (<code>XmlAttributeOverrides</code> initialization follows).

<pre><code>Type bankPayment = typeof(BankPayment);

XmlAttributes attributes = new XmlAttributes();
attributes.XmlElements.Add(new XmlElementAttribute(bankPayment.Name, bankPayment));

XmlAttributeOverrides overrides = new XmlAttributeOverrides();
overrides.Add(typeof(Order), "Payments", attributes);
</code></pre>

The appropriate <code>XmlSerializer</code> constructor would then be used.

NOTE: by doesn't work I mean the <code>InvalidOperationException</code> (<code>BankPayment</code> was not expected...) is thrown.

Can anyone shed some light on the subject? How would one go about and debug the issue further?

Use the XmlInclude or SoapInclude attribute to specify types that are not known statically

在使用.NET的XmlSerializer时，我遇到了一个非常奇怪的问题。以以下示例类为例：public class Order {    public PaymentCollection Payments { get; set; }    //everything else is serializable (incl...

问使用XmlInclude或SoapInclude属性指定静态未知的类型
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